Delta Airlines has recently changed the way they handle overbooked flights. If your flight is overbooked, you are told of the situation when you check-in, either online or at the airport kiosk, and are asked if you are willing to give up your seat and, if so, to enter a dollar amount corresponding to what it would take to get you to give it up. Not only does this provide the gate agents earlier information about likely volunteers so they can start rebooking, it lets Delta bump folks with the lowest opportunity cost of their time, likely saving the airline money and more efficiently allocating airline seats.
A very clever addition to the system first devised by Julian Simon decades ago.
Be sure to read the comments at that link, especially the Delta representative's further explanation.
(HT: My father.)